This disclosure generally relates to position or location approaches in GSM, CDMA, and UMTS networks. Further, this disclosure relates to user and control plane location approaches in core networks and GERAN, UTRAN, and Complementary Access radio access networks.
Mobile communications infrastructure is typically conceptualized in two generally separate components: the core network (“CN”); and the radio access network (RAN). Together, this infrastructure enables user equipment (“UE”), the RAN, and CN to be developed and implemented separately according to the permissive standards set by organizations such as 3GPP and ITU. Thus, various types of RANs, such as GERAN or UTRAN, can be paired with a single UMTS CN. Also, the UMTS standards provide for protocol separation between data related to user communications and data related to control of the network's various components. For example, within a UMTS mobile communications network, User Plane (“UP”) bearers are responsible for the transfer of user data, including but not limited to voice or application data. Control Plane (“CoP”) bearers handle control signaling and overall resource management.
As mobile networks transition towards 3G and beyond, location services (LCS, applications of which are sometimes referred to as Location Based Services, or LBS) have emerged as a vital service component enabled or provided by wireless communications networks. In addition to providing services conforming to government regulations such as wireless E911, LCS solutions also provide enhanced usability for mobile subscribers and revenue opportunities for network operators and service providers alike.
Position includes geographic coordinates, relative position, and derivatives such as velocity and acceleration. Although the term “position” is sometimes used to denote geographical position of an end-user while “location” is used to refer to the location within the network structure, these terms may often be used interchangeably without causing confusion. Common position measurement types used in mobile positioning or LCS include, but are not limited to, range, proximity, signal strength (such as path loss models or signal strength maps), round trip time, time of arrival, and angle of arrival. Multiple measurements can be combined, sometimes depending on which measurement types are available, to measure position. These combination approaches include, but are not limited to, radial (for example, employing multiple range measurements to solve for best agreement among circular loci), angle (for example, combining range and bearing using signal strength or round trip time), hyperbolic (for example, using multiple time-of-arrival), and real time differencing (for example, determining actual clock offsets between base stations).
Generally, LCS methods are accomplished through CoP or UP methods. CoP Location (“CoPL”) refers to using the control signaling channel within the network to provide location information of the subscriber or UE. UP Location (“UPL”), such as Secure User Plane Location (“SUPL”) uses the user data channel to provide location information. CoPL location approaches include, but are not limited to, Angle-of-Arrival (“AoA”), Observed Time-Difference-of-Arrival (“OTDoA”), Observed-Time-Difference (“OTD”), Enhanced-OTD (“E-OTD”), Enhanced Cell-ID (“E-CID”), Assisted Global Positioning System (“A-GPS”), and Assisted Galileo Navigation Satellite System (“A-GNSS”). UPL approaches include, but are not limited to, A-GPS, A-GNSS, and E-CID, where this position data is communicated over Internet Protocol (“IP”).
There are two established architectures associated with location determination in modern cellular networks. The architectures are Control Plane (“CoP”) and User Plane (“UP”) architectures. Typically location requests are sent to a network through a query gateway function 1. Depending on the network implementation CoP 15 or UP 10 may be used but not a combination of both, as shown in FIG. 1. Note that queries may also come directly from the target device itself rather than via a gateway. Similarly, CoP or UP may be used but not both.
The difference between user plane and control plane, strictly, is that the former uses the communication bearer established with the device in order to communicate measurements. The latter uses the native signaling channels supported by the controlling network elements of the core and access to communicate measurements. As such, a CoPL solution supporting A-GPS would use its control plane signaling interfaces to communicate GPS data to/from the handset. Similarly UPL can conduct E-OTD—the handset takes the timing measurements but it communicates them to the location platform using the data bearer.
UPL has the advantage of not depending on specific access technology to communicate measurement information. CoPL has the advantage that it can access and communicate measurements which may not be available to the device. Current models require network operators to deploy one or the other; CoPL or UPL.
Control Plane Location (“CoPL”) uses the native signaling plane of the network to establish sessions and communicate messages associated with location requests and to communicate measurements used for determining location. The control plane is the signaling infrastructure used for procedures such as call control, hand-off, registration, and authentication in a mobile network; CoPL uses this same infrastructure for performing location procedures. CoPL can utilize measurements made by both the control plane network elements as well as the end-user device being located.
FIG. 2A illustrates an exemplary architectural diagram of CoPL. A mobile station or mobile appliance 101 communication with a base transceiver station (“BTS”) 105 via wireless interface Um. A base station controller (“BSC”) 107 manages radio resources including the BTS 105 via an Abis interface. The Abis interface is an open interface completely defined as part of the ETSI specification for GSM and carries the call set up information, including voice channel assignments between the BSC 107 and BTS 105. A mobile switching center/visitor's location register (“MSC/VLR”) 113 coordinates between the mobile appliance communication network and a gateway mobile location center (“GMLC”) 117.
In operation, a location measurement device (not shown) may be connected to the BSC 107 via the Abis wire line interface and makes measurements on the RF signals of the Um interface, along with other measurements to support one or more of the position methods associated with the CoPL. Measurements from the location measurement units are sent to a servicing mobile location center (“SMLC”) 109 via BSC 107 where the location of an MS 101 can be determined. The BTS 105, BSC 107 and SMLC 109 form a base station subsystem (“BSS”) 103. The GMLC 117 is connected to a home location register (“HLR”) 111 over an Lh interface and the MSC/VLR 113 over an Lg interface. A gateway mobile switching center (“GMSC”) 115 is operably connected to the MSC/VLR 113 to allow interconnection with other networks.
The operation of a CoPL architecture is shown in FIG. 2B. This shows the 3GPP location services architecture. A gateway mobile location centre (“GMLC”) 117 is the network element that receives the location requests. The GMLC queries the HLR 111 over the Lh interface to find out which part of the access network 107 is currently serving the target device. The GMLC 117 sends a location request to the current serving core network node 113 via the Lg interface. The current serving core network node 113 (e.g., MSC or serving GPRS service node (“SGSN”)) then passes the request to the part of the access network 107 attached to the target device (e.g., GERAN BSC or UTRAN RNC). This access network element 107 then invokes the facilities of the SMLC 109. The location request session between the access network node 107 and the SMLC 109 provides a channel by which the SMLC 109 can ask for network measurements or to send messages to the end-user device 101 so that device measurement information can be exchanged. The SMLC 109 may also obtain location measurement information from external devices 110 such as location measurement units (“LMUs”) which take RF readings from the air interface. Similarly, the device may also take measurements from external systems, such as GPS satellites, and communicate these to the SMLC 109.
Developed as an alternative to CoPL, Secure User Plane Location (“SUPL”) is set of standards managed by the Open Mobile Alliance (“OMA”) to transfer assistance data and positioning data over IP to aid network and terminal-based positioning technologies in ascertaining the position of a SUPL Enabled Terminal (“SET”).
User Plane Location (“UPL”) does not explicitly utilize the control plane infrastructure. Instead UPL assumes that a data bearer plane is available between the location platform and the end-user device. That is, a control plane infrastructure may have been involved in establishing the data bearer so that communication can occur with the device but no location-specific procedural signaling occurs over the control plane. As such, UPL is limited to obtaining measurements directly from the end-user device itself.
SUPL includes a Lup reference point, the interface between the SUPL Location Platform (“SLP”) and SET, as well as security, authentication, authorization, charging functions, roaming, and privacy functions. For determining position, SUPL generally implements A-GPS, A-GNSS, or similar technology to communicate location data to a designated network node over Internet Protocol (“IP”).
FIG. 3A illustrates an exemplary architectural diagram for SUPL. The illustrated entities represent a group of functions, and not necessarily separate physical devices. In the SUPL architecture, an SLP 201 and SET 207 are provided. The SLP 201 may include a SUPL Location Center (“SLC”) 203 and a SUPL Positioning Center (“SPC”) 205. The SLC and SPC optionally communicate over the LIp interface, for instance, when the SLC and SPC are deployed as separate entities. The SET 207 generally includes a mobile location services (“MLS”) application, an application which requests and consumes location information, or a SUPL Agent, a service access point which accesses the network resources to obtain location information.
For any SET, an SLP 201 can perform the role of the home SLP (“H-SLP”), visited SLP (“V-SLP”) or emergency SLP (“E-SLP”). An H-SLP for a SET includes the subscription, authentication, and privacy related data for the SET and is generally associated with a part of the SET's home public land mobile network (“PLMN”). A V-SLP for a SET is an SLP selected by an H-SLP or E-SLP to assist in positioning thereof and is associated with or contained in the PLMN serving the SET. The E-SLP may perform positioning in association with emergency services initiated by the SET.
The SLC 203 coordinates operations of SUPL in the network and interacts with the SET over the User Plane bearer to perform various functions including, but not limited to, privacy, initiation, security, roaming, charging, service management, and positioning calculation. The SPC 205 supports various functions including, but not limited to, security, assistance delivery, reference retrieval, and positioning calculation.
SUPL session initiation is network-initiated or SET-initiated. The SUPL architecture provides various alternatives for initiating and facilitating SUPL functions. For example, a SUPL Initiation Function (“SIF”) is optionally initiated using a Wireless Application Protocol Push Proxy Gateway (“WAP PPG”) 211, a Short Message Service Center (“SMSC/MC”) 213, or a User Datagram Protocol/Internet Protocol (“UDP/IP”) 215 core, which forms user plane bearer 220.
The operation of UPL is shown in FIG. 3B. Secure User Plane Location is a standard specification for UPL. Location requests come to the SLP 201 from external applications or from the end-user device itself. If a data session does not exist between the SLP 201 and the device 207 already, then the SLP 201 may initiate a request such that an IP session (user plane bearer 220) is established between the device 207 and the SLP 201. From then on, the SLP 201 may request measurement information from the device 207. The device may also take measurements from the network 107 or from external systems such as GPS 210. Because there is no control plane connectivity to the network, the SLP 201 cannot directly request any measurement information from the network 107 itself. More information on SUPL, including the Secure User Plane Location Architecture documentation (OMA-AD-SUPL), can be readily obtained through OMA.